The trick is that damage bonuses are added to ALL attacks, not just attacks of the same type. However, an attack with multiple damage types has each soaked separately, so a piercing attack with a +12 bludgeoning bonus wouldn't see that +12 do anything unless the opponent had a bludgeoning soak of 12 or less, which basically does not exist after chapter two. However, noone soaks ethereal. It's something that confused me too at first.